Strophia ritchiei Maynard, 1894

Original Description

"STROPHIA RITCHIEI Novo.

Ritchie's Strophia.

FIG 41. A, front; B, side view of type.

DESCRIPTION.

            SP. CH. Size large. Shell, heavy. Striations, present. Whirls, ten. Examined, 1,000 specimens.

            Form of shell, inclined to be cylindrical; the first two whirls being equal in size and the third is but little smaller, and from this the shell slopes to a rather rounded point, forming an angle of sixty-five degrees.

            The striations are rather numerous, twenty-three to the first whirl, are regular, but not arranged in lines, about as wide as the interspaces between them, and although rounded and smooth, without furrows, are not polished.

            Aperture, not very small, and open. Lower tooth large and prominent, about .08 high, and about as wide at the base as it is high, and nearly one and one half times as long as high. Its position is central, and it is set back a little less than its length. Upper tooth represented by a slight tubercle.

            Margin, produced forward nearly as far as the diameter of the shell, and is slightly inclined to the right, slightly beyond the diameter of the shell. It is thin and rounded, but not protruded into any edge whatever. The frontal bar is extremely well developed, and so completely interrupts the striations that there is no trace of them within it.

            Color of the shell, dull white throughout, without markings of any kind. Within, flesh color, fading into white on the teeth and margin.

DIMENSIONS.

            Size of type, 1.37 by .57. Largest specimen, 1.37 by .65. smallest, 1.10 by .46. Greatest diameter, .65; smallest .46. Longest specimen, 1.40; shortest, 1.10.

OBSERVATIONS.

            The type form is very constant, pure individual variation being but slight. There is an inclination toward a more cylindrical form with the first three whirls equal, and some specimens show a slightly thickened margin, but as a rule, this is as in the type, and no thicker than the shell. The whirls vary in this form from ten to twelve. There are however, the following well-marked forms:

            No 1. About the form and size of the type, but with more numerous striations, twenty-five to the first whirl. The margin is thinner, with the edge sharpened, and the aperture smaller and more contracted. The color is ashy brown, with the striations creamy white, and the color within is rather dark, purplish brown. In this form there are individuals with slightly coarser striations, 20 to 22 to the first whirl. These usually have a thickened margin and a more cylindrical form. This form is not very common, being about one per cent of the whole.

            No.2 is a small form, 1.10 by .47, but with ten whirls, and with only sixteen striations to the first whirl, and the first three whirls are equal in diameter. Otherwise as in the type.

            No.3. Cylindrical, with eleven whirls, the first three of which are equal in diameter. The striations are a little less numerous than in the type, but the margin is rounded, but not thickened. There is a slight individual tendency in this form to assume, with fewer striations, the thin sharpened margin seen in the next species, S. grayi, but I can find no fewer than eighteen striations in any specimen, therefore it is the extreme form is not typical S. grayi. These are about one half per cent of the whole of this form.

            No. 4 is a remarkable form typically and, in fact, an incipient; species, but with two many gradations yet to permit a consistent naming. The general form is about that of typical S. ritchiei, but the aperture is wider and decidedly more open, but above all the striations are very numerous, thirty-four to the first whirl, and although they are narrow, they are so crowded as to be wider than the interspaces between them. The color is dull white, faintly tinted with flesh color within.

            This Strophia may be readily known by the large size, white color, projecting and thin margin, with its prominent frontal bar. There is a superficial resemblance to S. alba, but alba has a wider, more flaring, margin, with the edge rolled over and sharpened, and with the frontal bar not at all well developed. The central tooth is also small in alba, and set back from the bar about twice its width. From S. grayi it may be distinguished as given under that heading.

            I have named this fine, large Strophia for Mr. John Ritchie, Jr., of Boston, the well known conchologist and scientist, who, from the beginning, has exhibited the utmost interest in my work upon this genus.

HABITS AND DISTRIBUTION.

            Highburn Key lies to the eastward of what is known as the Middle Ground, an expanse of shallow water about thirty miles wide that stretches out toward the Atlantic from New Providence. The key is partly divided in two by bays which break into the land north and south ,hence forms a rude letter H, with a rather wide cross bar. Both the eastern and western arm of the key are made up of hills, but those to the eastward are higher and a little wider, than those to the westward.

            We entered the bay on the south of the key and landed near its head. Almost immediately upon looking about I saw specimens of Ritchie's Strophia. They were clinging to the stems of bushes and here occurred the typical form. I traced it back along the eastern hills northward for about a mile, a short distance beyond the ruins of the only building that stands on the key, and southward to the sonthern point of this division of the key, but at this point the brown form, No.1, was more prevalent, growing in the shade of the thicker shrubbery. Westward it spreads to the front of the hills of that division of the key but is not found on them. Thus it has quite an extended range, occupying about a half of a square mile, but it is no­where numerous, as compared with many other species of the genus.

            One of the most striking features of this species appears to be its powers of endurance. I have now a number of living specimens that were collected on Highburn Key on April 8th, 1893, that have been kept in a box in my cabinet. Last summer they gave me some trouble by wandering about over the other boxes, but have not attempted to move much since, but today, December 15th, I pierced the shell of one and found the animal, which is a pale horn color, lively, and it imme­diately shrunk back a whirl in from the broken portion of the shell, but did not form the usual partition. Although I put both this specimen and that of Cory's Strophia, of which I have spoken, in water, yet the animals have not as yet ventured out of their shells."

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